1. Field of the Invention
The present invention, in general relates to automotive testers and, more particularly, to an automotive coil tester.
An automotive coil boosts the voltage sufficient for it to create a spark that arcs across a spark plug which, in turn, ignites the fuel-air mixture as is well known in the automotive arts.
Coils, like all component parts, are prone to failure. The normal way to test a coil is to use an ohm meter to test the resistance of the internal windings. If the resistance falls within a given range it is assumed that the coil is not defective.
However, it is possible for coils to xe2x80x9cohm outxe2x80x9d with an acceptable resistance and still be defective. This creates an exasperating situation in which an automotive mechanic falsely believes that the problem cannot be due to a defective coil, because it ohms out properly, and therefore spends a great deal of time investigating and possibly even replacing other properly functioning component parts until all else has been exhausted. Finally in desperation, the mechanic may decide to replace the coil which then solves the problem.
As a result of a faulty test of the coil a great deal of time is spent troubleshooting and attempting repair in vain. Clearly, it is desirable to be able to ascertain with great accuracy whether a coil really is functioning properly.
Also, because coils can fail in a progressive manner in which they become weaker and weaker, it is not only desirable to determine whether or not a coil remains capable of boosting the voltage an amount sufficient to cause a spark to occur, but also determining how strong that spark is.
Whether or not the coil is removed from an automobile for testing, an additional variable exists. Is there sufficient voltage available to properly energize the coil? If for example the tester itself does not supply at least 9.0 volts to the coil, then the coil may fail to generate an adequate spark even if there is no defect in the coil itself.
Also, if the coil remains in the engine compartment during the test it will receive its power from the vehicle""s battery. It is also possible that the coil itself is not defective but that, for some reason, adequate power is not being supplied to the coil. It is important to determine if this is the situation.
Accordingly there exists today a need for an automotive ignition coil tester that can verify with certainty whether or not a coil is defective.
Clearly, such an apparatus would be a useful and desirable device, especially if it could do so quickly and inexpensively.
2. Description of Prior Art
Coil tester are, in general, known and include the ohm meters previously mentioned. While the structural arrangements of the above described devices, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.
It is an object of the present invention to provide an automotive ignition coil tester that is adapted to actuate a coil on demand.
It is also an important object of the invention to provide an automotive ignition coil tester that includes a push-button switch that can be depressed to actuate a coil.
Another object of the invention is to provide an automotive ignition coil tester that is adapted for use with a variable-length type of spark tester to determine the strength of spark that is produced.
Still another object of the invention is to provide an automotive ignition coil tester that includes circuitry for determining if a sufficient voltage is present to continue the test of the coil.
Still yet another object of the invention is to provide an automotive ignition coil tester that prevents the user from receiving a shock during testing.
Yet another important object of the invention is to provide an automotive ignition coil tester that is inexpensive to produce.
Still yet another important object of the invention is to provide an automotive ignition coil tester that provides a reliable indication of the state of functioning of an automotive coil.
Still one further object of the invention is to provide an automotive ignition coil tester that can be connected to a coil that is powered by a vehicle""s power supply and which remains disposed in the engine compartment during testing.
Briefly, an automotive ignition coil tester that is constructed in accordance with the principles of the present invention has a housing containing circuitry that includes a momentary single pole switch and a capacitor (also known as a condenser) that is wired across the contacts of the switch. One end of the switch goes to ground and another positive side goes to one end of a coil and eventually to a positive voltage source that is above 9.0 VDC. A first branch off the circuit goes from the positive side of the coil to a variable length spark tester. A second branch off the circuit goes from the positive side of the coil to a LED through a zener diode and resistor whereby the LED is illuminated sufficient to see only if at least 9.0 VDC is present. In use, illumination of the LED is first verified. Then the variable length spark tester is adjusted for a minimum voltage spark. The momentary switch is depressed and released while the variable length spark tester is observed to determine if a minimum spark is present. If it is not, the coil is deemed to be defective. If a spark is observed, the gap in the variable length spark tester is increased and the test is repeated until a maximum length of spark (i.e., arc) is determined sufficient to assess the quality of the coil. Accordingly, a coil that passes the basic test of functioning can further be assessed as one that is marginal and replaced as desired.